The Cognition Intervention Study Dortmund (CogniDo) and the Cognition Intervention Study Dortmund PLUS (CogniDo PLUS) investigated the short-term effects of having school lunch versus skipping it on children's basal (CogniDo) and executive (CogniDo PLUS) cognitive functions in the afternoon. The The Cognition Intervention Study Dortmund Continued (Coco) connected this two previous studies and investigates the effect of having school lunch versus skipping it on children's basal and executive cognitive functions later in the afternoon. The present study the Cognition Intervention Study Dortmund- Glycemic Index (CogniDo GI) examines the influence of the gylcemic index of lunch on cognitive performance of school children in the afternoon.